blood bank--- reviewing the basics - · pdf filegive blood. tm blood bank---reviewing the...

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Blood Bank---

Reviewing the basics

Virginia Hare, MT(ASCP)SBB

Immunohematology Reference Laboratory

American Red Cross Southern Region

Douglasville, Georgia

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Objectives:

Define the most commonly performed Blood Bank

tests and related terminology.

Discuss sample collection and routine pre-

transfusion testing.

Evaluate unexpected results and options for

transfusing patients in urgent situations.

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Sample Collection & Patient IDPatient Misidentification----Leading cause of transfusion fatalities

From CAP Website: “Mistransfusion occurs from

– -misidentification of the intended recipient at the time of collection of the pretransfusion testing sample,

– -during laboratory testing and preparation of units to be issued, and

– -at the time of transfusion.

– Misidentification at sample collection occurs approximately once in every 1,000 samples, and

– in one in every 12,000 transfusions the recipient receives a unit not intended for or not properly selected for him/her.”

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From CAP Today, January 2009

Dr. Richard Friedberg stated:

“ If the label’s wrong from the get-go, everything

else we do about accuracy and reliability and

precision goes out the window.”

From the Q-Probes study: one in 2,500 samples

has the WRONG BLOOD in TUBE.

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AABB Requirements for patient sample

identification and labeling in Stds. 25th ed.

Std. 5.11: Samples and Requests– “Identifying information for the patient and the blood sample shall

correspond and be confirmed at the time of collection using two

identifiers.”

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Patient sample ID and labeling-continued

AABB Std. 5.11.2▪ “Blood samples should be identified with an affixed label bearing sufficient

information for unique identification of the patient, including two

independent identifiers.”

▪ 5.11.2.1: “ The completed label shall be affixed to the tubes before the

person who drew the specimen leaves the side of the patient.”

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CAP-TRM.30575: Does the facility have a plan to

implement a system to reduce the risk of

mistransfusion for non-emergent red cell

transfusions?

Options:– Collect and test second sample

– Mechanical barrier

– Electronic ID system

– Another System to reduce risk

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Sample Age: AABB Std 5.13.3.2

“If the patient has been transfused in the

preceding 3 months with blood or a component

containing allogeneic red cells, has been pregnant

within the preceding 3 months, or the history is

uncertain or unavailable, a sample shall be

obtained from the patient within 3 days of the

scheduled transfusion. Day 0 is the day of draw.”

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Sample Age-Continued

Extended time limited by the type of sample

collected.

Refer to manufacturers instruction for reagents

used for compatibility testing.

– Time period for use of EDTA varies from 7 to 14 days.

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Patient History: AABB 5.13.5.

“There shall be a process to ensure that the

historical records listed below have been

reviewed and compared to current records

and that discrepancies have been

investigated and appropriate action taken

before a unit is issued for transfusion.”

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Patient History, continued

-Evaluation of patient

information

-Diagnosis

-Race

-Medication

-Transfusion history

-Transplant

-Pregnancy

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ABO Typing Reagents

– Monoclonal--only commercial source

– Check manufacturers instructions for clone information when

performing investigations

– Anti-A,B vs. Anti-A + -B

– Weak A Ag expression readily detectable by routine monoclonal

Anti-A reagents.

– New clone of anti-B does not routinely detect Acquired B.

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Reagent Red cells for reverse grouping

-Requirement to be Rh negative (D-)

-No requirements for other red cells antigens; they

could be M+ or Le(a+)

-Pool of at least 2 donors

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Common causes of ABO discrepancies

– Most discrepancies due unexpected antibody are due to Anti-A1

– 2nd most common is due to other cold reactive

antibodies (anti-M, Cold autoantibody)

– Most subgroups of A are routinely detectable

– -Seldom noticed unless there is a serum

grouping issue.

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Case 1-Where is the

discrepancy observed?

-Which is the most

probable cause of the

results observed?

-What can be done to

resolve it?

-What blood type should

be issued in an

emergency if discrepancy

not resolved?

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Case 1-continued

-Weaker that expected

reaction with A1 cell

-Subgroup of A ?

-Testing of A2, O red cell

and Auto Ctrl provide more

info.

-Until resolved, transfuse

Red Cells : group O

Plasma: group AB

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Case 2

-Where is the discrepancy

observed?

-Which is the most probable

cause of the results

observed?

-What can be done to

resolve it?

-What blood type should be

issued in an emergency if

discrepancy not resolved?

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Case 2-continued

-Weaker that expected rxn.

with A1 cell

-Subgroup of A or?

-Testing of A2, O red cell

and AC suggest the

presence of cold reactive

antibody

-Red Cells : group A

Plasma: group O

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Case 3

--Where is the discrepancy

observed?

-Which is the most probable

cause of the results

observed?

-What can be done to

resolve it?

-What blood type should be

issue in an emergency if

discrepancy not resolved?

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Case 3-continued

-Weaker that expected rxn.

with A1 cell; A2 negative

Subgroup of A ?

Testing of A2, O red cell

and AC suggest possible A

sub group.

Red Cells : group O

Plasma: group AB

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Routine Rh (D) typing testing requirements

AABB STD 5.13.2:

“Rh type shall be determined with anti-D reagent.

The test for weak D is unnecessary when testing

the patient.”

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Anti-D (Rho) Antisera

– Monoclonal reagents widely used

– Human polyclonal reagents still available

– Check manufacturers instructions for clone information when

performing investigations.

▪ Very useful information when resolving discrepancies.

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Anti-D: Unusual findings

Individuals previously typed D-; now type D+

I.S. reactivity that may not persist at 37C or IAT– i.e. Crawford, RhoHar

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Clones in Commercial Monoclonal Anti-D

Reagents

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D typing and Pregnancy

AABB STD 5.20.2: “Women who are pregnant or have

been pregnant recently shall be considered for Rh

Immune Globulin administration when all the following

apply:

1) The woman’s test for D Antigen is negative. A

test for weak D is not required.

2) The woman is not actively immunize to the D

antigen.”

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Case # 4

Patient typed as Rh negative during 2

pregnancies between 1985 and 1990.

Now: Anti-D Rh Ctrl– 2+ 0

Is additional needed?

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Case #4- continued

Was the correct patient collected?– Recollect and repeat typing.

Could the Rh typing be a false positive?– Results are valid. Testing performed at I.S. and Rh

Control is negative.

– Monoclonal anti-D is specific for D antigen. ▪ If testing performed with polyclonal anti-D, the presence of

antibody to a low frequency antigen is possible. Perform testing with a 2nd source of anti-D.

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Definition: Test used to demonstrate in-vivo coating of red cells with antibodies or complement, in particular IgG and C3d.

Antiglobulin reagents▪ Monoclonal

▪ Blends (rabbit IgG and monoclonal C3)

▪ Gel card contains Rabbit IgG

▪ Solid phase indicator cell is coated with monoclonal Anti-IgG

Direct Antiglobulin Test-DAT

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Strict adherence to critical test steps needed!

Wash RBCs at least 3 times without delay

Spin immediately after adding AHG

Resuspend and read immediately after spin.

When DAT is positive, what next?

Perform testing with anti-IgG and anti-C3 reagents to determine the sensitizing protein

.

DAT- Testing reminders

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Definition: Method to free and recover antibody from sensitized red cells.

When to perform an eluate:

– DAT is positive with IgG

– DAT is negative- in certain instances when trying to explain decrease red cell survival

Time period to perform?

– “Recently transfused” patients, which is commonly defined as transfused within the last 14 days. In other labs, this period is extended to 21 days.

Elution

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Not considered to be an antibody enhancement reagent

Does not provide commonly accepted level of sensitivity

Due to the molecular size, Rh antibodies may react stronger in albumin compared to salinemethods.

Albumin

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Advantages:

Detects most potentially clinically significant blood group antibodies.

Less sensitive than PEG for detection of warm reactive autoantibodies.

May facilitate identification of antibodies demonstrating reactivity at 37oC phase of testing. Anti-Lea, -Leb, -M and -N and other direct agglutinins may be identified using this method.

LISS-additive for tube testing

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Disadvantages:

Less sensitive than gel or PeG/IAT in detection of some clinically significant blood group antibodies and warm reactive autoantibodies.

Enhanced detection of most cold reactive autoantibodies.

LISS-additive for tube testing

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Advantages:

Detects most potentially clinically significant blood group antibodies.

Uses smaller volumes of serum and reagents.

Reactions are stable for up to 24 hours.

Standardized procedure for improved consistency.

GEL: Column agglutination technology

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Disadvantages:

Somewhat less sensitive for detection of some alloantibodies.

Enhanced detection of warm reactive autoantibodies.

Requires special equipment and reagent preparation.

GEL: Column agglutination technology

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Provides stable, well-defined endpoints of the reaction.

Enhanced sensitivity makes the detection of weak alloantibodies easier.

Ease of use.

No predilution of reagents is required.

Standardized procedure for improved consistency when manufacturer’s panels are tested.

Solid Phase: Advantages

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Requires a centrifuge that can spin microplates.

Requires a 37°C incubator for microplates.

Requires a light source for reading the final results (non-automated method).

Increased sensitivity may detect weak autoantibodies that other systems do not.

Solid Phase: Disadvantages

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Case # 5

18 y.o. male with sickle cell disease

-Admitted with acute chest syndrome

-No history of transfusion at your facility

Results of antibody screen with LISS:– 37C IAT

– SC I 0 2+

– SC II 2+ 4+

– SC III 0 3+

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Comparison of antibody screening results: LISS vs. PEG:

LISS

– 37C IAT PEG/IAT

– SC I 0 2+ 3+

– SC II 2+ 4+ 4+

– SC III 0 3+ 4+

Which method is most informative?

Case # 5-continued

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Comparison of antibody screening results: LISS vs. PEG:

LISS– 37C IAT PEG/IAT

– SC I 0 2+ 3+

– SC II 2+ 4+ 4+

– SC III 0 3+ 4+

More about this case later.

Case # 5-continued

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Antibody identification (Ab-ID)

Method to identify specificity (ies) of antibodies detected by antibody screen.

Approaches vary based on

-staff expertise,

-available resources, and

-urgency of patient’s transfusion need.

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Standard panel (full):

– Designed to identify commonly encountered specificities.

– Resolves most routine antibody problems.

– Provides limited information for complex problems or when multiple specificities have been previously identified.

Extended panels: 10 vs. 16 cell panels designed to help separate multiple specificities

Ab-ID: Standard Panel vs. Selected panel

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Panel of cells selected using available information:

– Ab screen results, pt. history, pt. phenotype

Requires use of multiple panels and some experience and/or software to create

Maximizes information obtained with the least amount of sample and testing.

Ab-ID: Selected cell panel

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Case # 5 continued…...

LISS

– indicates the presence of >1 antibody

– will probably identify one antibody specificity

Additional testing: auto control? DAT?

– Phenotype the patient’s red cells?

– Routine or selected cell panel? ▪ Anti-E + -Fya are identified

– Rule out of additional alloantibodies: PEG?

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Automation

Available instruments capable of performing most BB tests.

Routinely used for basic testing: ABO-Rh, antibody screening. Ab–ID also available.

Methodologies used:

– Gel

– Solid phase

– Hemagglutination

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Automation

Advantages:Minimizes hands-on time

Positive sample identification

Standardizes testing

Records easily archived

Disadvantages:

TAT can be greater than manual testing

Flexibility for STAT testing varies▪ May detect unwanted antibody or antibody of undetermined specificity

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In closing….

Be observant and inquisitive.

Use available resources to aid in problem resolution:

– patient, family, clinical staff, literature, manufacturers, colleagues, internet…….

Advancements occur everyday in Transfusion Medicine…..

Be an active participant!

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If you have questions or comments, feel free to contact me at

harev@usa.redcross.org

Phone: 770-852-4376